1. Field Of The Invention
The present invention relates to medical prosthetic devices and more particularly relates to an improved ocular prosthetic device having improved tissue compatibility and attachment. Even more particularly, the present invention relates to an improved total ocular replacement that has muscle attachment sites upon the surface of a polymeric implant, the attachment sites in between the remaining outer surface coating that discourages muscle attachment.
2. General Background
Current ocular replacement implants and conformers often produce ocular complications and cosmetic defects, such as a sagging lower eyelid, poor movement relative to the fellow eye, implant extrusion or migration as well as potentially fatal orbital infections.
Prior total ocular replacement prosthetic devices have generally consisted of non-biocompatible materials that do not adequately interface between the implant and the surrounding muscles and tissues. Metal meshes, prongs, clamps, clips and pins allow significant mechanical erosion between the implant and tissues due to physical compliance differences.
Prior art devices generally suffer from a lack of selective ingrowth when a biocompatible material is used in the implant design. Muscles and tissues adjacent to a biocompatible porous material (whether synthetic or donor tissue) will indiscriminately ingrow and scar down on to it. The scarring and ingrowth can constrict the movement of the implant. This also produces a problem if the implant needs to be removed at a future date for medical reasons. In many cases the prosthesis cannot be removed without removing a significant amount of muscular tissue as well.
Other devices suffer from a lack of an implant design that has the biomechanics to move the implant in a natural appearing way. To do so all the extra-ocular muscles should be attached to the prosthesis in their anatomically correct positions.
Another problem of prior art total ocular replacements is a lack of adequate co-operative movement of the cosmetic conformer with the follow eye. To have this there should be a direct connection between the cosmetic conformer and the implant. All designs that have any such connection do not have an effective method of keeping the conjunctiva closed around the connection. In addition, wear on the unsecured conjunctiva at the connection point produces thinning and retraction of it thereby providing an entrance for pathogens into the orbital space.
A number of prior art devices have been disclosed in patents. These patents have dealt with the need to attach the extra-ocular muscles which have been removed from the diseased eye to the circular-shaped implant replacing the eye. The attachment is necessary for the two reasons: 1) to help anchor the implant into the orbit and 2) to transmit movement to the implant so that it can respond similarly as the eye did. However, prior art designs generally have attachment means for only the four (4) rectus muscles and do not include the two oblique muscles. In addition, the attachment means while varying in style result in several detrimental conditions for the muscles.
Patents by Rolf (U.S. Pat. No. 2,516,804), Rosen (U.S. Pat. No. 2,661,480) and Cutler (U.S. Pat. No. 2,649,590) all teach the use of a ring (generally metal) that the muscles are wrapped and sutured around. This type of attachment means creates friction and wear on the muscles where the ring rubs against them.
The Allen et al. patent (U.S. Pat. No. 2,653,327) teaches imbricating the muscles over the anterior area of the implant. Imbrication (overlapping the tendinous ends of two opposing muscles and suturing them together such that the four rectus muscles are sutured together in a roman cross shape) results in the four rectus muscles scarring down together into one larger mass anterior to the implant which severely restricts their range of motion.
Patents issued to Stone (U.S. Pat. No. 2,660,732), Jardon (U.S. Pat. No. 2,571,721), and Moulton (U.S. Pat. No. 2,667,645) all use a metal mesh over the entire anterior portion of the implant which the muscles are attached to by sutures and various metal clips.
Jardon (U.S. Pat. No. 2,629,877), Noelle (U.S. Pat. No. 2,617,994) and Gordon (U.S. Pat. No. 5,026,392) all disclose the use of synthetic tabs of the ends of the muscles to act as the attachment means to the implant. Jardon '877 sutures the muscles to metal clips which fit into tunnels in the implant; Noelle '994 uses all metal meshes and clips; Gordon '392 uses both synthetic polymers and metals. Gordon's muscles attachment sites are movable in only one plane of the implant.
The Clarke U.S. Pat. No. 2,634,423 uses horizontal and vertical metal pins to keep the muscles in place.
Jardon (U.S. Pat. No. 2,688,139) describes a completely porous implant. However, this construction allows for scarring cellular attachment along the entire length of the muscles attached restricting their strength and range of motion.
Jardon '139 and '721 and Cutler '590 describe the use of a shaft protruding out of the implant for use of transmitting the implants motion to the cosmetic conformer. Cutler's patent uses a detachable pin that is inserted post-operatively into the implant and the rear of the conformer. The Jardon U.S. Pat. Nos. 2,571,721 and 2,629,877 each disclose an attached shaft that protrudes from the implant; however, it does not have porous material on the shaft itself for close apposition of the conjunctiva.